The present invention relates to a method of manufacturing a heat exchanger suitably used as an evaporator of a car air conditioner, which is a refrigeration cycle to be mounted on an automobile, for example.
A heat exchanger which is used for an evaporator of a car air conditioner has been known (Japanese Patent Application Laid-Open (kokai) No. 2003-214794). The known heat exchanger includes a pair of header tanks disposed apart from each other, and a plurality of heat exchange tubes which are disposed between the two header tanks and whose opposite end portions are connected to the corresponding header tanks. At least one of the header tanks is composed of a first tank constituting member to which the heat exchange tubes are connected, and a second tank constituting member which is joined to the first tank constituting member and which covers one side of the first tank constituting member opposite the heat exchange tubes. The two tank constituting members have plate-shaped portions which are laminated to form a lamination portion. In the lamination portion composed of the two plate-shaped portions, claws provided on the first plate-shaped portion disposed at one end with respect to the lamination direction are passed through elongated through-holes which are formed in the other or second plate-shaped portion and which extend in the longitudinal direction of the header tanks. Each claw is engaged with the outer surface (with respect to the lamination direction) of the second plate-shaped portion at one end of the corresponding elongated hole with respect to the longitudinal direction. In this state, the plate-shaped portions of the two tank constituting members which constitute the corresponding header tank are brazed together.
The heat exchanger disclosed in the publication has been manufactured by a method which includes forming elongated holes (through-holes) in the second plate-shaped portion of one tank constituting member such that the longitudinal direction of the elongated holes coincides with the longitudinal direction of the header tanks; laminating the plate-shaped portions of the two tank constituting members; and punching the first plate-shaped portion of the other tank constituting member so as to simultaneously form elongated holes (through-holes) whose longitudinal direction coincides with the longitudinal direction of the header tanks, and a claw at one end of each elongated hole. The claw engages with the second plate-shaped portion, whereby the two tank constituting members are provisionally fixed together.
However, the method of manufacturing a heat exchanger disclosed in the publication has a problem in that, when claws are formed, cracks may be formed in the claws and the claws may break, which decreases the joint strength of the two tank constituting members provisionally fixed together.